A student needs the first and last quiz result.
What You Need to Understand
Indexes identify list positions: zero means the first element, one the second, and negative indexes count backward from the end. An empty list has no valid element indexes.
When to Use It
A student needs the first and last quiz result.
Step-by-Step Python Example
scores = [78, 92, 85]
print(scores[0])
print(scores[-1])
print(scores[-2])How the Example Works
The results are 78, 85 and 92. Negative indexing is convenient when list size changes.
Example Output
78
85
92
apple appleA Second Example
Compare this smaller variation with the main example, then experiment with your own values.
fruits = ["pear", "apple", "orange"]
print(fruits[1], fruits[-2])Important Behavior and Edge Cases
Do not assume scores[len(scores)] is valid; the last valid positive index is len(scores)-1.
Try It Yourself
Read the second item from the beginning and the second from the end of a five-item list.
Common Beginner Mistakes
- Do not assume
scores[len(scores)]is valid; the last valid positive index islen(scores)-1. - Assuming every sequence operation modifies the original data or that a tuple makes nested mutable objects immutable.
Key Takeaways
- Indexes identify list positions: zero means the first element, one the second, and negative indexes count backward from the end.
- The results are 78, 85 and 92.
- Do not assume
scores[len(scores)]is valid; the last valid positive index islen(scores)-1.